In recent years, for reducing the thickness and weight of an electronic device, improving the portability of the electronic device, and preventing breakage of components in the electronic device, a housing has been required to have increased rigidity. Specifically, when the electronic device is held with one hand and operated with the other hand, when the electronic device is transported, or when a monitor or the like is opened or closed, a biased load is applied, and therefore a force acts on the housing in a torsion direction. In addition, if the electronic device is dropped by accident during transportation, a force also acts in a torsion direction. Therefore, the housing is required to have high torsional rigidity. In view of such a background, many techniques for increasing the rigidity of a housing have been heretofore proposed.
Specifically, Patent Document 1 discloses an invention for increasing the rigidity of an electric device cabinet structure which includes a resin lower case having upper and lower electric device mounting surfaces, and an upper case having a front wall overlapping the upper electric device mounting surface. Patent Document 2 discloses an invention for increasing the rigidity of an electronic device housing of by making the electronic device housing have a structure in which surfaces of two plates are selectively bonded and joined together. Patent Document 3 discloses an invention for increasing the rigidity of an electronic device housing by abutting the tip of a rib, which is formed on the inner surface of a first housing, against the inner surface of a second housing.